Many gas turbine engines use a heat exchanger or recuperator to increase the operating efficiency of the engine by extracting heat from the exhaust gas and preheating the combustion air. Typically, a recuperator for a gas turbine engine must be capable of operating at temperatures of between about 500 degrees C. and 800 degrees C. and internal pressures of between approximately 140 kPa and 1400 kPa under operating conditions involving repeated starting and stopping cycles.
Such recuperators include a core which is commonly constructed of a plurality of relatively thin flat sheets having an angled or corrugated spacer fixedly attached therebetween. The sheets are joined into cells, sealed and form passages between the sheets. These cells are stacked or rolled and form alternate air (recipient) cells and hot exhaust (donor) cells. Compressed discharged air from a compressor of the engine passes through the air cell while hot exhaust gas flows through alternate cells. The exhaust gas heats the sheets and the spacers, and the compressor discharged air is heated by conduction from the sheets and spacers. The need for repeatability of construction of each cell assures that the final recuperator is economically and easily assembled. Examples, of such repeatability required includes length, height, thickness, weld size, weld position, weld splatter and others.
An example of such a recuperator is disclosed in U.S. Pat. No. 5,060,721 issued to Charles T. Darragh on Oct. 29, 1991. In such a system, Darragh discloses a heat exchanger having been used to increase the efficiency of the engine by absorbing heat from that exhaust gases and transferring a portion of the exhaust heat to the combustion air. The heat exchanger is built-up from a plurality of performed involute curved cells stacked in a circular array to provide flow passages for the donor fluid and the recipient fluid respectively.
Thus, to economically and functionally produce such a recuperator, used with gas turbine engines, requires a process which insures an effective and repeatable procedure. For example, to assure the stacking of a fixed number of cell within a preestablished curricular configuration the height and thickness is extremely critical. To further insure the position and location or each cell within the recuperator structure, the position of individual passages within the cell needs to be accurate to insure for efficient functional operation.
The present invention is directed to overcoming one or more of the problems as set forth above.